1. Field of the Invention
The present invention relates to an apparatus and a method for measuring a temperature of a living body. More particularly, the present invention relates to a non-invasive apparatus for measuring an internal temperature of a living body by measuring the electromagnetic wave characteristics of a medium, and a method therefor.
2. Description of the Related Art
In order to detect and treat an abnormal state of a human body, a non-invasive apparatus and a method for measuring a temperature of a living body by measuring microwaves emitted from the living body have been developed. When the temperature of a medium is greater than absolute zero, electromagnetic waves are emitted according to a principle of black body radiation. If the medium is a living body, electromagnetic wave signals are emitted from the inside of the living body to the outside of the skin of the living body. The temperature of abnormal tissues, which is higher than the temperature of normal tissues, can be detected by measuring the electromagnetic waves emitted from a predetermined portion of the living body and converting the measured electromagnetic waves into a temperature, so that an abnormal state of the living body may be detected at an early stage.
FIG. 1 is a functional diagram of a conventional apparatus employing a microwave radiometer to measure the temperature of a specimen according to the prior art.
Referring to FIG. 1, a specimen 100 emits electromagnetic radiation 102 having a certain intensity and frequency-spectrum distribution, each of which is a function of the temperature of the specimen 100 and the characteristics of the material the specimen 100 is composed of. The frequency-spectrum distribution includes a portion of a microwave interval to which a microwave antenna unit 104 is responsive. The temperature of the specimen 100 is sensed by the microwave antenna unit 104, which is positioned in a cooperative spatial relationship with the specimen 100 to receive part of electromagnetic radiation 102, which is within this microwave interval.
A microwave radiometer 105, including a microwave receiver 106, a reference microwave noise source 108, and a temperature meter 110, compares the relative intensity of the microwave noise output from the microwave antenna unit 104 with respect to the intensity of the output from the reference microwave noise source 108. The temperature of the specimen 100 is indicated by the temperature meter 110 in response to the output from the microwave receiver 106 applied as an input thereto.
The conventional apparatus for measuring a temperature of a living body stores a temperature conversion table, established from a temperature conversion graph, with respect to a specific medium as shown in FIG. 2. The conventional apparatus determines temperatures according to the measured emitted intensities.
Referring to FIG. 2, the emitted intensity and the temperature are in a linearly proportional relationship. In other words, as the emitted intensity increases, the detected temperature increases linearly. Thus, a specific temperature corresponding to a specific emitted intensity can be selected. However, the graph of FIG. 2 may be applied only to a predetermined portion of a living body having a specific permittivity or conductivity. If the permittivity or the conductivity is changed within the living body, it is preferable to use an alternate graph.
As shown in FIG. 3, radiation power, i.e., received electric power, emitted at the same temperature may vary when the permittivity or the conductivity is different so that errors occur in the conversion process of a measured emitted intensity into a temperature by using a single temperature conversion table.
For example, if a received electric power measured at a predetermined portion of a living body having a permittivity of 49.8 is 4xc3x9710xe2x88x9216 W, a converted temperature according to the graph f1 is 46.5xc2x0 C. However, a converted temperature for the same electric power according to the graph f2, which represents a predetermined portion of a living body having a permittivity of 9.8, is 38xc2x0 C., so that a difference of 8.5xc2x0 C. occurs.
For example, in a case where the temperature of breasts that have large deviations of the permittivity and the conductivity from 9.8 to 51.3 S/m and 0.37 to 3.4 S/m, respectively, is measured, the deviation of emitted intensity due to the differences of the permittivity and the conductivity cannot be corrected using a single temperature conversion table. Accordingly, a large deviation occurs in the converted temperature. As a result, abnormal tissues may be determined as normal tissues thereby preventing the detection of an abnormal state in a living body.
In an effort to solve the above and related problems, it is a feature of an embodiment of the present invention to provide an apparatus and a method for measuring an internal temperature of a living body with improved reliability.
To provide this feature of an embodiment of the present invention, an apparatus for measuring a temperature of a portion of a living body includes a signal receiving unit for receiving electromagnetic wave signals emitted from the portion of a living body to be measured, a signal processing unit for processing the electromagnetic signals input from the signal receiving unit and outputting a radiation power signal, a medium characteristic measurement unit for measuring a value of a conductivity or a permittivity of the portion of the living body to be measured and for outputting the measured value, and a temperature conversion unit, including a computer database for storing a plurality of temperature conversion tables with respect to radiation power according to the conductivity or the permittivity of the portion of the living body, for determining a corresponding temperature using the measured value of the conductivity or the permittivity of the portion of the living body and the radiation power signal of the signal processing unit.
The signal receiving unit preferably includes a receiver for receiving the electromagnetic signals and a transmission line for sending the electromagnetic wave signals from the receiver to the signal processing unit. It is also preferable that the receiver is an antenna or a probe.
The signal processing unit preferably includes an amplifier for amplifying the electromagnetic wave signals input from the signal receiving unit, a filter for extracting a signal value of a predetermined frequency band from the electromagnetic wave signals, a noise source for maintaining a reference signal of a specific temperature, a switch for switching the extracted signal and the reference signal within a specific interval and for connecting to a next stage, an isolator for processing the extracted signal in one direction and matching circuits, and a detector for detecting an enveloped curve of the extracted signal.
The temperature conversion unit preferably includes an information storage unit having a computer database for storing the plurality of temperature conversion tables with respect to radiation power, and an information processing unit for selecting a proper temperature conversion table corresponding to the conductivity or the permittivity measured by the information storage unit and for determining the temperature corresponding to the radiation power signal of the electromagnetic wave input from the signal processing unit, from the temperature conversion tables.
The medium characteristic measurement unit preferably includes a signal generator for generating an electromagnetic wave signal of a specific frequency band, a transmitter for sending the electromagnetic wave signal to the portion of the living body, a receiver for receiving the electromagnetic wave signal passed through the portion of the living body to be measured, a signal processor for receiving the electromagnetic wave signal from the receiver and processing the received signal, and a controller for controlling the signal generator and the signal processor.
The receiver preferably receives the electromagnetic wave signal reflected on the portion of the living body to be measured.
It is preferable that the apparatus further includes a display for displaying the temperature selected by the temperature conversion unit.
To provide another feature of an embodiment of the present invention, a method for measuring a temperature of a portion of a living body includes receiving electromagnetic wave signals from the portion of a living body to be measured, processing the received electromagnetic wave signals and extracting a radiation power signal therefrom, measuring medium characteristics, such as a conductivity or a permittivity, of the portion of the living body to be measured, and converting a temperature for determining the temperature of the portion of the living body based on the radiation power signal of the received electromagnetic wave signals and the conductivity or the permittivity of the measuring medium characteristics process.
Processing the received electromagnetic signals preferably includes removing noise from the electromagnetic wave signals, extracting the electromagnetic wave signal of a specific frequency band, and amplifying the extracted signal value.
Measuring medium characteristics preferably includes radiating the electromagnetic wave signal of a specific frequency band to the portion of the living body to be measured, receiving the electromagnetic wave signal passed through the portion of the living body to be measured, and calculating a conductivity or a permittivity based on the received electromagnetic wave signal.
Converting a temperature preferably includes selecting a specific temperature conversion table corresponding to the conductivity or the permittivity from a plurality of temperature conversion tables with respect to radiation power, which are previously stored, and calculating a specific temperature corresponding to the radiation power of the electromagnetic wave from the temperature conversion table.
In operation, the present invention stores a temperature conversion table corresponding to a permittivity or a conductivity in a radiometer as a computer database, and measures the permittivity or the conductivity of a medium. Thereafter, the measured electromagnetic wave is converted into a temperature with reference to the temperature conversion table corresponding to the measured constant. Therefore, when measuring the internal temperature of a living body, reliability of the measured temperature is improved.